Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Mumble - Mumble is an open source, low-latency, high quality voice chat software primarily intended for use...
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
Discord - Step up your game with a modern voice & text chat app. Crystal clear voice, multiple server and channel support, mobile apps, and more.
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
RaidCall - Free & Light. Setting up is fast and easy; with no need to rent or set up servers. Low CPU usage and minimum memory footprint allows for smooth, uninterrupted communication. im. Group Communication.